This invention relates to a technique for monitoring arc and corona discharge in high voltage generators and more particularly to a method of employing film for monitoring arc and corona discharge in high voltage power supplies.
As one can ascertain, high voltage power supplies are widely employed in the electronics and industrial fields. These supplies normally generate tens of thousands of volts and are utilized, for example, to supply operating potential to cathode ray tubes, in high power transmitters and numerous other applications. For an example of the uses of high voltage power supplies, reference is made to a text entitled "Principles of Solid State Power Conversion" by Ralph E. Tarter, published by Howard W. Sams & Company (1985). As one can ascertain, such high voltage power supplies are associated with the generation of extremely high voltages. Based on the high voltages involved, substantial arcing and corona discharge can occur in supply operation due to the electrical breakdown of gas, air or dielectric which surrounds the components utilized in such supplies.
Essentially an arc is a continuous luminous discharge of electricity which can occur across an insulating medium and essentially is characterized by a voltage drop in an immediate vicinity of the point that the arc occurs to another point in which the arc is directed.
A corona discharge is a luminous discharge which is due to the ionization of the air surrounding a conductor which is caused by a voltage gradient exceeding a certain critical angle. Such corona discharges can also occur in a gas filled environment causing a discharge with a slight luminosity which is produced in the neighborhood of a conductor without greatly heating the conductor and is usually limited to the regions surrounding the conductor in which the electric field exceeds a certain value. In any event, due to the extremely high voltages that these supplies are designed to operate at, such supplies experience both corona and arc discharge if proper precautions are not taken.
It is apparent that both effects are normally due either to a malfunction in the power supply or an inherent design deficiency which essentially results in corona and/or an arc discharge. The design defect or malfunction can occur in many ways. For example, such power supplies utilize printed circuit boards whereby components are placed in terminal areas on the board and then soldered to the board. In any event, in a high voltage power supply, the soldering of components should be carefully implemented and one cannot have, for example, extending sharp projections when implementing solder joints. These projections form potential arc points whereby an arc can be directed from the solder joints to other areas involved with the power supply or vice versa. The nature of an arc or corona is such that it is completely random and can occur based on spacing, heating and other factors as well. In any event, it is desirable to note the exact location of the arc so as to make a determination of where the arc occurred in the supply to enable the designer or user of the supply to make the necessary repairs in order to assure that such a malfunction does not occur again.
The present state of the art equipment which is available operates to measure electrical field stresses in a high voltage power supply such as corona and/or arcs. This apparatus is limited to measuring the EMI (electromagnetic interference) which provides external fields relating to arcs and coronas and as they affect the input leads to the power supply. This type of measurement is extremely difficult to quantify and does not pinpoint the internal source or location of the arc or corona. In any event, the prior art techniques, as indicated above, which includes equipment to measure such events really monitors the input power leads to the power supply to determine whether or not there are high frequency components present which high frequency components are normally generated by the creation of arc or corona discharges.
These techniques, as briefly described, do not pinpoint or indicate to the designer or user the location of the arc. Hence, by using prior art techniques one knows that an arc has occurred but does not know where the arc emanated from.
One can also ascertain that due to the nature of an arc or corona discharge the entire operation may be extremely intermittent and may not occur on a continuous basis. An arc or corona discharge may be a function of the humidity, the temperature and various other factors which will cause the creation of the arc or corona discharge. Hence, one may experience arcs or arc events in high voltage power supplies which are relatively random and do not continuously occur. The prior art equipment for measuring such techniques makes the measurement of such random events extremely difficult, if not impossible, and as indicated above does not allow the designer or user to determine the exact location of the arc.
It is therefore an object of the present invention to provide a method for determining arc and corona discharge in a high voltage power supply.
It is a further object of the present invention to utilize a photographic film, which is placed at strategic locations throughout the power supply, which film will become exposed upon the generation of a corona or an arc discharge to allow a designer or user to accurately and precisely determine the location of the arc, as well as to quantify the extent and magnitude of the arc.